Acute pulmonary edema (APE) and interstitial emphysema is a naturally-occurring disease of cattle and the disease syndrome can be reproduced experimentally by intraruminal administration of L-tryptophan (TRP) or by intraruminal or intravenous doses of 3-methylindole (3MI). 3MI causes pulmonary lesions in cattle, goats, and some other species. Prior research has shown that ruminal microorganisms convert TRP to indoleacetic acid (IAA) which is decarboxylated to 3MI. The microorgansism responsible for the formation of 3MI from IAA is a Lactobacillus sp. and this organism appears to also be present in the large intestine of many species. 3MI is rapidly metabolized by the animal and metabolites are excreted in the urine primarily as 3-methyloxindole derivatives. Cytoxic effects are observed in alveolar Type I and non-ciliated bronchiolar lining cells within 30 minutes after 3MI administration and metabolism of 3MI by the mixed function oxidase system (MFO) is apparently responsible for pulmonary toxicity. We are investigating the specific reactions and/or metabolites of 3MI which are responsible for the development of pulmonary lesions and we intend to isolate and identify the urinary 3MI metabolites in several species. We plan to relate species differences in the pathways of 3MI metabolism with species differences in the pulmonary toxicity. A major objective will be to confirm the involvement and identify the chemical nature of highly reactive metabolic intermediates which are postulated to cause lung damage. This will be accomplished using in vitro and in vivo experiments related to metabolite formation and covalent binding of 3MI metabolites in various tissues and organs. Later experiments will be designed to assess the risk of 3MI exposure in man. We will analyze for the presence of 3MI metabolites in thh urine of subjects and determine whether metabolism of 3MI by human lung tissue results in the formation of toxic metabolites.